Fabrics are utilized in numerous situations requiring strength, flexibility and durability. For example, fabrics are often used in the construction of containers for storing and/or transporting granular or powder materials, as well as in the construction of shelter for goods, equipment, people, and the like. Traditionally, fabrics have been constructed of natural fibers; however, in recent years synthetic fibers manufactured from polypropylene or other plastics have come into extensive use since they are generally stronger and more durable than fabrics made of natural fiber.
Characteristics of fabrics in general make their use undesirable in some circumstances. For example, many granular and even liquid materials develop a static-electric charge through friction as they are poured into, discharged from or vibrated within a receptacle. However, since fabrics are not electrically conductive, discharge of static-electricity from such materials contained by fabric receptacles is difficult, if not impossible, posing the danger of explosion or fire caused by an electrical spark. Fabrics also cannot be used in applications requiring an air or moisture-tight barrier due to their fibrous nature. Plastic fabrics, in particular, are also highly susceptible to degradation caused by ultraviolet light and therefore cannot be used in direct sunlight, for example, without incurring a substantial reduction in their flexibility and strength.
In an effort to eliminate the foregoing combination of undesirable characteristics, fabrics manufactured of plastic fibers have been covered with a metallic laminate such as foil made of aluminum or other electrically conductive metal. This approach involves securing the foil to one side of the synthetic fabric by means of a suitable adhesive. The laminated fabric may then be used to construct a receptacle, for example, with the foil laminate comprising the interior surface of the receptacle, thereby providing an electrically conductive surface through which the electrical charge can be discharged to an appropriate ground. The foil laminate may also be applied to portions of the synthetic fabric which will be exposed to ultraviolet light, thereby acting as a reflector to substantially reduce the amount of ultraviolet light contacting the fabric and the resultant degradation thereof. Use of foil laminates has also proved to be initially effective in reducing the transmission of gas and moisture through the underlying fabric.
Foil laminates in the past, however, have proven susceptible to abrasion, tearing and separation from the underlying fabric over a period of time, particularly along the edges of the foil laminate. For example, foil laminates used to cover the interior surface of fabric receptacle will often tear or separate from the underlying fabric due to abrasion from the contents of the receptacle as the receptacle is filled, emptied or transported. The cumulative effect of such abrasion quickly reduces the effectiveness of the foil layer as a grounding surface and often results in unwanted contamination of the contents of the bag with foil particles or flakes. In addition, damage to the foil laminates through normal wear and tear or due to handling of materials reduces the ability of the fabric to inhibit the passage of moisture and air and the ability of the laminate to protect the fabric against degradation from ultraviolet light.
The present invention comprises a highly durable metalized fabric which overcomes the foregoing disadvantages associated with foil-laminated fabrics. The metalized fabric includes a supporting layer of plastic fabric to which a layer of plastic film having an outer metalized surface is secured. In one embodiment, the plastic film is secured to the underlying fabric by extrusion lamination. The resulting metalized surface of the fabric is electrically conductive, resistant to degradation by ultraviolet light and is substantially air and moisture tight.